There was a deafening boom, and then she was submerged within the waters she had craved to be one with her whole life, and suddenly everything made sense. There's always a siren, singing you to shipwreck. Some of us may be more susceptible than others are, but there's always a siren. It may be with us all our lives, or it may be many years or decades before we find it or it finds us. But when it does find us, if we're lucky we're Odysseus tied up to the ship's mast, hearing the song with perfect clarity, but ferried to safety by a crew whose ears have been plugged with beeswax. If we're not at all lucky, we're another sort of sailor stepping off the deck to drown in the sea.
Her best friend had just been killed before her eyes, and she couldn't bring herself to fight the siren's song and swim back to the surface for the air that her lungs starve for. So she gave in, and sunk down the the depths below.